SAINT LOUIS (June 25, 2014) -- The bottom’s up in round 5 of the 2014 U.S. Junior Closed Championship.

Heading into the round, the standings’ top-three leaders had begun to break away, separating themselves from the rest of the field by a full point -- but on Tuesday those front-runners were suddenly reminded: Not so fast. The bottom three players in the standings combined for three points, while the top three scored just a half-point.

Tournament leader IM Jeffrey Xiong was dealt his first defeat after getting bit by IM Sam Sevian, the second seed and pre-tournament favorite who had lurked dangerously in the bottom of the standings after finding three losses through the first four rounds. Sevian looked like his old self for at least Tuesday, patiently squeezing out Xiong’s Sicilian by positionally strangling him right from the start.

Also slipping was the tournament’s lone GM Kayden Troff, who fell with the white pieces in his first loss of the event to FM Michael Bodek. The two front-runner defeats gave a serious shake to the standings just past the halfway mark, moving Bodek up with Troff in second place, and allowing IM Luke Harmon-Vellotti to catch pace in front after mustering the day’s only draw to FM Justus Williams.

The back of the standings saw a good shuffle as well on Tuesday: FM Arthur Shen took out some frustrations rather convincingly against FM Josh Colas, while NM Matt Larson -- the tournament’s wildcard and lowest-seed -- drummed up a fantastic win over IM Aleksandr Ostrovskiy. The players enjoy a rest day on Wednesday.

There weren’t many fireworks in Bodek’s upset over Troff on Tuesday, just simply a slow push back against the grandmaster until he toppled. In fact, Troff looked to achieve what he wanted out of the opening, earning a small advantage in a Catalan. On the surface, Bodek’s 15...Qg5 looked questionable, immediately chased by Troff’s 16. h4 to seemingly isolate the black queen -- though it ultimately proved to unbalance the position.

“I thought Qg5 was a pretty dynamic move,” Bodek said. “I couldn’t really be trapped -- at most pushed around a lot -- but it put pressure on those pawns in the middle. I thought it was a good move, though who knows what the computer will say. It definitely forced the issue.”

Pushing around the black queen may have served as part of white’s fall, as Troff’s 19. Bf3 chased her away -- though blocked f4 as a defender to white’s e5 pawn. It allowed Bodek to reroute, finding two moves backwards including 20...Nd7 to win the overextended pawn on the next move.

Troff immediately bailed from the game, forcing liquidation and driving action toward an endgame with opposite-colored bishops. The inclusion of active rooks, however, gave Bodek the advantage.

“I was very happy once we went into a position with opposite-colored bishops,” Bodek said. “Even though it could have meant a draw, it also meant I could push as long as I wanted and couldn’t lose the position. I was worried that I might overlook some fortress, but aside from that, it’s just play calm chess and improve my position. The only time I had to calculate was deciding when to trade rooks.”

The major pieces came off on the 42nd move, revealing Bodek’s king in a monstrous position that fatally disrupted white’s kingside unit.

Larson, having earned his wildcard as a promising local to the host Chess Club and Scholastic Center of Saint Louis, entered the tournament more than a 150-point underdog to the next-closest competitor -- though the 17-year-old has more-than proven he can hang just fine in this elite field.

Larson, who has only been playing chess for four years, scored the highest-rated draw of his career against Xiong in round 3 -- and on Tuesday he notched the highest-rated victory of his career over Ostrovskiy, who outweighed the newcomer by more than 300 rating points.

Larson looked comfortable against Ostrovskiy’s Slav after 4. dxc4, offering a gambit in exchange for white’s strong central control. Ostrovskiy looked to hold his material advantage with 5...b4, but Larson’s 6. b3 further strengthened the white setup, who soon controlled several dangerously open lanes on the queenside. By 11. Nc3, white was ahead in development by several tempe and ready for attack, ushering Ostrovskiy’s first long-think to deal with the impending danger.

Black never found comfort in the game, its forces being shoved backward thanks to white’s central control and its king never finding time to castle. And Ostrovskiy found no more comfort from his clock, which was down to 3 minutes before his 23rd move -- and Larson with a half-hour left.

Ostrovskiy’s 22...cxd4 grabbed a second pawn toward a material advantage, but its exchange of even more tempo brought white’s attack with a full head of steam. Larson’s 28. Rxf7 was the doomsday sacrifice, fully opening black’s defense and bringing a quick end.

“When you’re the lowest-rated player, people feel like they have an obligation to win,” Larson said. “Like Jeffrey Xiong, the other day, played crazy and was losing an endgame that he would never lose to someone like Kayden (Troff).

“I think I just had a good position for the whole game today, and I just kept pressing. It feels good; if my opponent had just blundered and I was up a piece or something, it wouldn’t be as satisfying.”

Shen had just a half-point to show for his solid efforts through the first four rounds of the tournament, several times not finding fruit from clear-winning positions. Against Colas on Tuesday, he saw things through to a convincing end.

His fifth-round match lasted just 21 moves and was likely over well before then, after going hyper-aggressive in an open Sicilian. Colas’ questionable opening consisted of two early moves by the queen -- and seven by pawns through the first 10 moves. His 10. b4 was one too many.

Shen’s fantastic 11. Nd5 offered a sacrifice of the piece in exchange for a vicious attack against black’s drastically underdeveloped king. His 13. c4 beckoned yet another pawn move out of Colas and allowed another open lane for Shen, who brought a second rook into the attack.

By 19. Qxa6, Shen had won back three pawns for his knight and completely owned the queenside -- though he was no longer seeking material.

“I didn’t necessarily prepare Nd5 before the game, but it’s always an idea,” Shen said. “I guess it did look a little dubious, and I’m not sure if that sac was sound, but I’m having a hard time believing white’s not winning there. When he played b4, it just felt wrong to me.

“I felt like I had to play it; this tournament was already not going so well for me, so I thought I’d have some fun. It looked like a position I liked to play.”

Wednesday is a rest day. The 2014 U.S. Junior Closed will resume for the sixth round on Thursday at 1:00 p.m. CT and continue through June 29. Every round is streamed live on www.uschesschamps.com with commentary, analysis and player interviews by GM Ben Finegold and FM Aviv Friedman.